Cambodia's opposition leader in exile is criticizing the country's government, accusing it of blatantly interfering with attempts to prosecute crimes committed by the Khmer Rouge.

Sam Rainsy told VOA's Khmer service Thursday that officials in the government of Prime Minister Hun Sen "fear a serious investigation."

"Any serious and in-depth investigation would show that several members of the current government were involved in the Khmer Rouge crimes," said Sam Rainsy. "It is why several members of the current government have refused to testify to respond to summons."

Khmer Rouge tribunal judge Laurent Kasper-Ansermet quit in protest earlier this week, citing repeated challenges to his authority by his Cambodian counterpart on the tribunal. Kasper-Ansermet's predecessor, Swiss Judge Siegfried Blunt, quit the tribunal earlier this year after complaining of similar interference from You Bunleng.

Sam Rainsy said unless such interference ends, the tribunal's legacy will be one of continued violence.

"If all the people who are, who were responsible for the death of millions of people are not duly prosecuted, then subsequent leaders will feel free to kill other people like the current government is doing," he said.

The tribunal has already sentenced one former Khmer Rouge official to life in prison, and is currently hearing a second case against the group's three top surviving leaders. The trio face charges of war crimes and crimes against humanity in the deaths of some 1.7 million Cambodians who died under Khmer Rouge rule in the 1970s.

Prime Minister Hun Sen, himself a former Khmer Rouge member, has repeatedly said there should be no further prosecutions. He and other Cambodian officials have voiced fear that further cases could spark civil war in the tiny Southeast Asian nation.

Opposition leader Sam Rainsy is in the United States meeting with officials from both the U.S. and United Nations.

He says many U.S. and U.N. officials compare Cambodia and Burma, but that unlike Burma, Cambodia is going in the wrong direction.

"The leader of the opposition is not allowed to go back to Cambodia, is not allowed to take part in any election because of a politically subservient court that has sentenced the opposition leader, preventing him to go back and preventing him from running," said Rainsy.

Sam Rainsy called on the U.S. and the U.N. to push for free and fair elections in Cambodia, saying corruption and incompetence are eroding the standard of living for many Cambodians.

Last year, a Cambodian court sentenced Sam Rainsy in absentia to two years in prison on charges of defaming Foreign Minister Hor Namhong.

Sam Rainsy, who is living in exile in France, already faced 12 years in prison on two previous convictions which his supporters charge are politically motivated.

Sam Rainsy supporters charge the cases were brought to prevent him from leading his party into elections expected in 2013.